1. Technical Field
Example embodiments of the present invention relate in general to a method of transmitting channel rank information (RI) through a physical uplink shared channel (PUSCH) in a Third Generation Partnership Project (3GPP) long term evolution (LTE) and LTE-advanced system, and more specifically, to a method of transmitting channel RI when the number of bits for transmitting the channel RI to be transmitted through a PUSCH is three.
2. Related Art
In 3GPP TS 36.211 v9.0.0 and 3GPP TS 36.212 v9.0.0 of 3GPP LTE release 8/9, a maximum of four transmitter antennas are used for downlink multiple-input multiple-output (MIMO) data transmission.
Assuming that there are two transmitter antennas, a terminal determines a value of {1, 2} as RI of a downlink channel matrix and feeds the 1-bit RI back to a base station. Also, assuming that there are four transmitter antennas, a terminal determines a value of {1, 2, 3, 4} as RI of a downlink channel matrix and feeds the 2-bit RI back to a base station. In 3GPP TS 36.212 v9.0.0, a standard has been only defined for a method of encoding and transmitting RI when the RI is one bit (i.e., a case where there are two downlink antennas) or two bits (i.e., a case where there are four downlink antennas).
However, in 3GPP LTE-advanced following 3GPP LTE release 10 that is a standard after 3GPP LTE release 8/9, a maximum of eight transmitter antennas are used for downlink MIMO data transmission. In following standards, the number of transmitter antennas may further increase to improve a data transmission rate.
For example, when there are eight transmitter antennas, a terminal should determine a value of {1, 2, 3, 4, 5, 6, 7, 8} as RI of a downlink channel matrix and feed the 3-bit RI back to a base station.
Furthermore, in standards following 3GPP LTE release 8/9, it has been determined to use carrier aggregation whereby successive or non-successive carrier bands are aggregated and used. In this case, channel RI about several carrier bands should be fed back from a terminal to a base station, and thus the number of bits of channel RI that should be transmitted may further increase.
Meanwhile, in a 3GPP LTE system and LTE-advanced system, terminals transmit control information to a base station through a PUSCH or physical uplink control channel (PUCCH), and channel RI is encoded by repetition coding and transmitted through the PUSCH.
However, as described above, a case in which the number of bits for transmitting channel RI is three or more is not taken into consideration at all in current 3GPP LTE release 8/9. Consequently, a method of encoding and transmitting channel RI when the number of bits of channel RI is three or more is necessary for 3GPP LTE release 10 or the following standards.